In shale reservoirs, crude oil always involves a varying percentage of methane gas that may greatly affect the properties and the migration behavior of crude oil. In this work, to evaluate the effect of methane gas and to clarify the molecular mechanisms, the migration of oil/gas mixture in shale channels was characterized using molecular dynamics (MD) simulations. Specifically, the transport of oil with different methane fractions in a shale inorganic nano-pore throat was simulated. With analyzing the force that the oil undergoes when going across the nano-pore, the oil dynamic transport feature for different methane fractions was clarified. Then, the interfacial tension, the diffusion coefficient, and the interaction energy were calculated to give insights into the methane effects on oil transport. In addition, other oil-associated gases (ethane and propane) and the effect of temperature were studied and discussed. This work expands our knowledge of the oil and gas transport in nano- pore throat at the molecular level, and it is expected to facilitate future studies on the migration of fluids through space-confined channels.

Zhang, Zhang, Y., Yu, J., Su, Y., Du, Y., Liu, Z., 2020. A comparison of -alkane contents in sediments of five lakes from contrasting environments. Organic Geochemistry 139, 103943.

http://www.sciencedirect.com/science/article/pii/S0146638019301809 n In paleolimnology studies, the trajectories of -alkane abundances and distributions in dated sediments are widely used indicators of changing environmental and ecological status in the overlying water over time. n However, the factors contributing to the variable -alkane profiles of lake systems are not yet fully understood. n Here, a comparative study was conducted to examine natural and anthropogenic influences on the sediment - alkane profiles of five representative lakes in China. Core samples from the deep oligo- mesotrophic lakes Fuxian and Lugu (FX-1 and LG-1 cores), the shallow eutrophic lakes Taibai and Changdang (TB-1 and CD-1 n cores) and the alpine Lake Heihai (HH-1 core) were used. While there were striking differences in -alkane n abundances and distributions between the cores, the results suggested that the -alkanes in all five studied lakes were derived mainly from biogenic sources, rather than from petroleum contamination. The short-chain ( C -alkane profiles of 21 n different cores varied significantly. Abundances of long-chain -alkanes (C , C and C ) in HH-1 were 29 31 33 approximately 3 - 7 times greater than in other cores. Coupled with the lowest Paq (average 0.29) values n recorded in the study, this indicates a predominantly terrestrial plant origin for the >C -alkanes, most likely 21 the dense alpine meadow which surrounds the lake. In other cores, however, aquatic macrophytes appear to be n more important contributors of the -alkanes, a result that corresponds with the relatively low density of terrestrial plants in those catchments.

Zhao, B., Li, R., Qin, X., Liu, F., Wu, X., Zhao, D., Liu, Q., Zhou, W., 2019. Characteristics of shale reservoirs in the Upper Paleozoic Shanxi Formation, Central Ordos Basin. Acta Sedimentologica Sinica 37, 1140-1151.

http://www.cjxb.ac.cn/EN/abstract/abstract4054.shtml Shanxi Formation shale is a stratum of marine-continental transitional facies with potential for shale gas exploration in the Ordos Basin. The petrology, mineralogy,reservoir space,pore structure and reservoir quality of the shale show that Shanxi Formation shale comprises black mud shale,grey-black mudstone and dark grey silty mudstone. It mainly consists of 59.6% clay minerals and 36.9% quartz,on average. Fractures are classified into macroand microfractures;the latter mainly occur in the shale and organic macerals, with an average surface density of 116.6/m. In addition to mineral and diagenetic pores,organic pores occur in organic macerals,formed by hydrocarbon generation as a result of the high degree of thermal evolution. Shanxi Formation mud shale has -3 2 an average porosity of 0.77% and an average permeability of 0.06×10 μm .A positive correlation was found R between total organic carbon (TOC), vitrinite reflectance( ) and clay mineral content;quartz content and shale o porosity are negatively correlated. The general development of fractures increases the permeability of